The invention relates to improvements in manuals for electronic organs and analogous musical instruments. More particularly, the invention relates to improvements in manuals wherein selected keys are depressible about substantially horizontal axes against the opposition of springs or like yieldable means and wherein such depression involves a greater effort during the initial stage and a less pronounced effort during the next-following stage or stages of depression.
When the key of a piano is depressed, the player must exert a force which suffices to overcome the inertia of the associated hammer and certain other movable parts of the corresponding action. Moreover, the player senses a dynamic sliding of such movable parts relative to each other. Many electronic organs and analogous musical instruments have manuals which are designed in such a way that each key must be depressed against the opposition of a spring which offers a fixed resistance to depression and returns the key to its non-depressed position as soon as the application of finger pressure upon the key is terminated. Thus, the nature of resistance which is offered by the keys of the manual in an organ is quite different from the nature of resistance which is offered by piano keys. Consequently, it invariably requires a certain period of time for a piano player to become accustomed to the touch of keys in the manual of an electronic organ and vice versa.
German Auslegeschrift No. 24 26 106 of Aliprandi discloses a manual for electronic organs which is designed to produce a so-called piano effect, i.e., whose manipulation creates the impression of depressing the keys of a piano. To this end, Aliprandi proposes to place a pivotable reaction lever adjacent each key of the manual and to provide each key with a rigid, rotary or elastic pusher which can pivot the reaction lever in response to depression of the key. The lever has a cam face which is designed in such a way that the lever initially offers a rather pronounced resistance to pivoting from its starting or idle position but such resistance decreases as the depression of the respective key progresses. The lever is biased by a torsion spring so that it normally assumes its starting position and reassumes such position as soon as the depression of the corresponding key is terminated. The arrangement is such that only one component of the force which is required to depress a selected key is used to pivot the associated reaction lever from its starting position. Moreover, the mass of the reaction lever is small or very small, especially when compared with the mass of parts which must be displaced in response to the depression of a piano key. Lack of mass is compensated for by the utilization of strong springs which bias the reaction levers to their starting positions; such strong springs contribute to the overall cost of the manual. Another drawback of the manual of Aliprandi is that the reaction force of each lever is independent of the acceleration (change of velocity) of the respective key during movement of the key from the non-depressed toward the depressed position.